[willamette-fcst] Forecast - Tuesday, March 17th, 2009

[Willamette Valley Ag/Burning Forecast]

Daily Smoke Management Forecast




Oregon Department of Agriculture
Smoke Management Program
Weather Outlook and Field Burning Advisory for Willamette Valley Growers and Fire Districts.

Issued: 
     Tuesday, March 17th, 2009 at 9:00am.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from now until 4:30pm.
     Straw stack burning is allowed, for dry stacks, from now until 4:30pm.

Weather Discussion:
     A cool and unstable air mass combined with strong onshore
     flow to bring vigorous shower activity to Washington and
     Oregon Monday.  Some showers contained small hail Monday
     afternoon with the snow level dropping as low as 1000 feet
     in the coast range overnight.  Much of western Oregon
     received between one-quarter and one-half inch of rain, from
     the showers, on Monday.

     Considerable snow fell in the Cascades Monday.  On Mt. Hood,
     Timberline lodge picked up 9 inches of new snow, with 11
     inches reported at Mt. Hood Meadows.  Mt. Bachelor reported
     17 inces of new snow, since Monday morning.  ODOT cameras
     revelaed snow-packed Cascade passes this morning, from
     Government Camp to Willamette Pass.  Snow levels remain
     quite low this morning, with snow falling in the higher
     elevations of the coast range and over the Cascade passes. 
     There was even a fresh layer of slush reported on Sunset
     Summit (Hwy 26), over the northern coast range.

     Satellite imagery this morning showed an enhanced area of
     cloudiness rotating onshore into northwestern Oregon, likely
     associated with a strong westerly jet stream.  Doppler radar
     showed considerable showers over northwestern
     Oregon...mainly from Corvallis northward.  A few rain and
     snow showers were also being reported over central and
     eastern Oregon, in spite of the strong rain shadow effect,
     due to the strong westerly flow aloft flowing across the
     Cascades.  The freezing levels over Salem and Medford were
     measured at just 3300 and 4900 feet respectively early this morning.

     Showers should taper off across the southern half of Oregon
     this afternoon, as the jet stream begins to migrate
     northward.  However, the air mass aloft should remain cold
     enough to maintain shower activity across northern Oregon. 
     Western Oregon temperatuers were in the low to mid 40s at
     mid morning.  The ODa surface analysis showed southerly
     gradients and winds could still become rather blustery near
     showers today.  Valley highs should only climb into the low 50s.

Surface Winds:
     S 10-15 G25 this morning, SW 5-15 G20 this afternoon.
Transport Winds:
     SSW 25 this morning, SW 20 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 5000 feet.  Ventilation index 125.
High Temperature:
     Salem\'s high temperature today will be near 52.
Humidities:
     Minimum relative humidity will be near 63%.
Sunrise/Sunset:
     Salem sunset tonight: 7:21pm; sunrise tomorrow: 7:18am.

Extended Outlook:
     The jet stream is forecast to shift northward, to over
     southern British Columbia, tonight and Wednesday.  A warm
     front, moving north into Washington, will lift snow levels
     above the Cascade passes Wednesday, as the precipitation
     tapers off.  A weak cold front will sag southward...renewing
     the threat of light rain across mainly northwestern Oregon
     by Thursday afternoon.  The jet stream is forecast to drop
     southward, over Oregon, Friday.

     A cold front will bring rain and drop the snow levels below
     the Cascade passes by Friday afternoon.  A cool, showery air
     mass will swing onshore Saturday with a transitory ridge
     bringing some drying Sunday, but snow levels will remain
     below the Cascade passes.  Another cold front is forecast to
     renew the rain and mountain snow by Monday afternoon,
     folowed by more cool showers Tuesday.  There is some
     indication that a stronger upper-level ridge may begin
     building over the region about Wednesday of next week, for
     warmer and drier conditions.

Tomorrow (18 Mar):  Mostly Cloudy and Warmer.  Snow Level Lifting to 4-5000 Feet. 40/57

Thu (19 Mar):  Mostly Cloudy.  Chance of Rain...Mainly North.  Snow Level 6000 Feet.  40/59

Fri (20 Mar):  Increasing Rain and Mountain Snow.  Snow Level 4-5000 Feet.  43/54

Sat (21 Mar):  Showers.  Snow Level 3000 Feet.  40/52

Sun (22 Mar):  Decreasing Showers.  Snow Level 3000 Feet.  37/52

Mon (23 Mar):  Increasing Rain and Mountain Snow.  Snow Level 3-4000 Feet.  37/52

Tue (24 Mar):  Showers.  Snow Level 2-3000 Feet.  37/51

ODA Meteorologist
weather at oda.state.or.us